3. Sort the expression in the light blue box into one of the three categories.
Variable Variable Expression Numerical Expression
82 + w
g - 6
30/p
17 - 2 + 5
24 + 2 x 4
y
x
k
m 18s
(5 + 9)/7
4. There are different ways to express multiplication and
division.
Multiplication: Different ways to show four times y.
4(y)
4 • y
4y (The number is always written before the variable.)
(4)(y)
4 x y (Try to avoid 4 x y because you may confuse the
variable x and the times symbol x.)
Division: Different ways to show twelve divided by n.
12/n
12 ÷ n
5. VOCABULARY
Evaluate – to evaluate a variable expression, you write the
expression, substitute (replace) a number for each variable, and
simplify.
EVALUATING EXPRESSIONS
What is the Area of this triangle?
A =
1/2bh Variable Expression
A = 1/2(4)
(12) Substitute numbers
for variables
12cm A = 24 cm
2
Simplify
4 cm
6. Example 1: Identify the variable. Evaluate the variable expression when y = 3.
A. 27y B. -12/y + 8
27y -12/y + 8
27(3)
-12/3 + 8
-4 + 8
81
4
Click to
reveal
answer
Click to
reveal
answer
7. Example 2: Find the area of a triangle if the base is 5 cm and the height is 4 cm. Remember to label!
A = (5)(4)
A = (20)
A = 10 cm
2
1
2
1
2
drag the red check to the yellow check to reveal the answer